The preparation of overbased calcium or barium salts of carboxylic acids, alkyl phenols, and sulfonic acids are disclosed in the following U.S. Pat. Nos. 2,616,904; 2,760,970; 2,767,164; 2,798,852; 2,802,816; 3,027,325; 3,031,284; 3,342,733; 3,533,975; 3,773,664; and 3,779,922. The use of these overbased metal salts in the halogen-containing organic polymer is described in the following U.S. Pat. Nos. 4,159,973; 4,252,698; and 3,194,823. According to the teachings of U.S. Pat. No. 4,665,117, light colored alkali or alkaline earth metal salts are prepared where alkyl phenol is used as a promoter.
With the movement to replace heavy metals in various compositions, liquid calcium products have been developed. Low metal concentrations, poor compatibility and haziness in clear products have severely limited the universal acceptance of calcium based liquid compositions. Problems are encountered in the stability of these compositions upon standing or storage. Storage stability is due to the incompatibility among the metal salts employed in the composition and is exhibited by increased turbidity, viscosity, or insoluble solids over time.
As a result, the liquid calcium compositions are no longer homogeneous or readily pourable and must be specially treated in order to be used. U.S. Pat. No. 5,322,872 is directed to stabilized compositions of mixed metal carboxylates having improved storage stability. According to this patent, a complexing agent is added to the mixed metal carboxylate in order to improve shelf stability. Complexing agents disclosed in this patent include phosphines, phosphites aromatic cyanides, aromatic hydroxy compounds, oximes and other compounds. U.S. Pat. Nos. 5,830,935 and 5,859,267 have also issued as directed to processes for improving the basic metal composition.
U.S. Pat. Nos. 3,766,066 ('066) and 3,766,067 ('067) disclose the preparation of solid calcium-containing micellar complexes from homogenized carbonated calcium overbased organic acid salts with the aid of “conversion agents” such as water and alcohols. The '067 patent teaches that to prepare the desired micellar complexes from the overbased salts it is first necessary to subject a solution of those salts in inert organic liquid diluents to a homogenization step with vigorous agitation in the presence of water, alcohols or mixtures of alcohols and water. The homogenization is accompanied by a “thickening” or “gelling” phenomenon to produce crystalline particles characterized by an x-ray diffraction pattern corresponding to that of calcite. However, x-ray diffraction studies of the starting salt solutions do not indicate the presence of any crystalline calcium carbonate. In fact, the '066 patent teaches that the calcium carbonate present in the starting non-homogenized solution appears to be amorphous. The amorphous metal salts or complexes present in the material are unquestionably transformed to crystalline particles on homogenization according to the '066 and '067 patents. U.S. Pat. No. 5,534,169 also teaches the conversion of a Newtonian overbased calcium carboxylate to a non-Newtonian dispersion of calcite particles in order to produce a material useful for reducing friction. U.S. Pat. No. 5,830,832 also discloses the preparation of powdered calcium overbased soaps from branched oxo-acids.
Overbased metal components have been used in lubricant compositions. For example, overbased metal sulfonates have normally been used as detergents. Notwithstanding the state of the art as exemplified by the above patents and the current state of the art, there is a need for further improvements in the use of overbased alkaline earth metal salts in lubricating oil compositions.